android 10+从后台启动 Activity 的限制

限制后台启动activity

如果未满足相关条件，则后台不允许启动activity，并会打印如下相关的log：

// anything that has fallen through would currently be abortedSlog.w(TAG, "Background activity start [callingPackage: " + callingPackage       + "; callingUid: " + callingUid       + "; appSwitchState: " + appSwitchState       + "; isCallingUidForeground: " + isCallingUidForeground       + "; callingUidHasAnyVisibleWindow: " + callingUidHasAnyVisibleWindow       + "; callingUidProcState: " + DebugUtils.valueToString(ActivityManager.class,      "PROCESS_STATE_", callingUidProcState)       + "; isCallingUidPersistentSystemProcess: " + isCallingUidPersistentSystemProcess       + "; realCallingUid: " + realCallingUid       + "; isRealCallingUidForeground: " + isRealCallingUidForeground       + "; realCallingUidHasAnyVisibleWindow: " + realCallingUidHasAnyVisibleWindow       + "; realCallingUidProcState: " + DebugUtils.valueToString(ActivityManager.class,          "PROCESS_STATE_", realCallingUidProcState)       + "; isRealCallingUidPersistentSystemProcess: "       + isRealCallingUidPersistentSystemProcess       + "; originatingPendingIntent: " + originatingPendingIntent       + "; allowBackgroundActivityStart: " + allowBackgroundActivityStart       + "; intent: " + intent       + "; callerApp: " + callerApp       + "; inVisibleTask: " + (callerApp != null && callerApp.hasActivityInVisibleTask())       + "]");

限制的例外情况

在 Android 10 或更高版本上运行的应用只有在满足以下一项或多项条件时，才能启动 Activity：

ROOT_UID/SYSTEM_UID/NFC_UID等重要uid

final boolean useCallingUidState =        originatingPendingIntent == null || checkedOptions == null                || !checkedOptions.getIgnorePendingIntentCreatorForegroundState();.......if (useCallingUidState) {    if (callingUid == Process.ROOT_UID || callingAppId == Process.SYSTEM_UID            || callingAppId == Process.NFC_UID) {        if (DEBUG_ACTIVITY_STARTS) {            Slog.d(TAG,                    "Activity start allowed for important callingUid (" + callingUid + ")");        }        return false;    }    ......

home 进程

        if (useCallingUidState) {          ......            if (isHomeApp(callingUid, callingPackage)) {                if (DEBUG_ACTIVITY_STARTS) {                    Slog.d(TAG,"Activity start allowed for home app callingUid (" + callingUid + ")");                }                return false;            }

Ime窗口所在uid下的进程

        if (useCallingUidState) {         ......            // IME should always be allowed to start activity, like IME settings.            final WindowState imeWindow = mRootWindowContainer.getCurrentInputMethodWindow();            if (imeWindow != null && callingAppId == imeWindow.mOwnerUid) {                if (DEBUG_ACTIVITY_STARTS) {                    Slog.d(TAG, "Activity start allowed for active ime (" + callingUid + ")");                }                return false;            }

应用具有可见窗口，例如前台 Activity

应用是persistent系统进程，并正在执行UI操作

// 是persistent系统进程，并正在执行UI操作final boolean isCallingUidPersistentSystemProcess =        callingUidProcState <= ActivityManager.PROCESS_STATE_PERSISTENT_UI;// 如果允许应用程序切换，则允许具有可见应用程序窗口的普通应用程序启动活动，// 或者将允许具有非应用程序可见窗口的动态壁纸等应用程序。final boolean appSwitchAllowedOrFg =        appSwitchState == APP_SWITCH_ALLOW || appSwitchState == APP_SWITCH_FG_ONLY;final boolean allowCallingUidStartActivity =        ((appSwitchAllowedOrFg || mService.mActiveUids.hasNonAppVisibleWindow(callingUid))        && callingUidHasAnyVisibleWindow)        || isCallingUidPersistentSystemProcess;if (useCallingUidState && allowCallingUidStartActivity) {    if (DEBUG_ACTIVITY_STARTS) {        Slog.d(TAG, "Activity start allowed: callingUidHasAnyVisibleWindow = " + callingUid                + ", isCallingUidPersistentSystemProcess = "                + isCallingUidPersistentSystemProcess);    }    return false;}

应用声明了START_ACTIVITIES_FROM_BACKGROUND 权限

特权system/priv-app/目录下的app才可以申请豁免

<!-- @SystemApi @hide Allows an application to start activities from background --><permission android:name="android.permission.START_ACTIVITIES_FROM_BACKGROUND"android:protectionLevel="signature|privileged|vendorPrivileged|oem|verifier|role" />

        if (useCallingUidState) {            // don't abort if the callingUid has START_ACTIVITIES_FROM_BACKGROUND permission            if (mService.checkPermission(                    START_ACTIVITIES_FROM_BACKGROUND, callingPid, callingUid)                    == PERMISSION_GRANTED) {                if (DEBUG_ACTIVITY_STARTS) {                    Slog.d(TAG,"Background activity start allowed: START_ACTIVITIES_FROM_BACKGROUND "        + "permission granted for uid "        + callingUid);                }                return false;            }

应用是Recent组件所在uid下进程（这里一般为home进程）

        if (useCallingUidState) {        .......            // don't abort if the caller has the same uid as the recents component            if (mSupervisor.mRecentTasks.isCallerRecents(callingUid)) {                if (DEBUG_ACTIVITY_STARTS) {                    Slog.d(TAG, "Background activity start allowed: callingUid (" + callingUid+ ") is recents");                }                return false;            }

应用是设备所有者

应用是在设备所有者模式下运行的设备政策控制器。示例用例包括完全托管的企业设备，以及数字标识牌和自助服务终端等专用设备。

        if (useCallingUidState) {          ......            // don't abort if the callingUid is the device owner            if (mService.isDeviceOwner(callingUid)) {                if (DEBUG_ACTIVITY_STARTS) {                    Slog.d(TAG, "Background activity start allowed: callingUid (" + callingUid+ ") is device owner");                }                return false;            }

应用通过 CompanionDeviceManager API 与配套硬件设备相关联。

此 API 支持应用启动 API，以响应用户在配对设备上执行的操作。

        if (useCallingUidState) {           ......            // don't abort if the callingUid has companion device            final int callingUserId = UserHandle.getUserId(callingUid);            if (mService.isAssociatedCompanionApp(callingUserId,                    callingUid)) {                if (DEBUG_ACTIVITY_STARTS) {                    Slog.d(TAG, "Background activity start allowed: callingUid (" + callingUid+ ") is companion app");                }                return false;            }

用户已向应用授予 SYSTEM_ALERT_WINDOW 权限

**注意：**在 Android 10（Go 版本）上运行的应用无法获得SYSTEM_ALERT_WINDOW权限。
注意：如果应用程序以 API 级别 23 或更高级别为目标，则应用程序用户必须通过权限管理屏幕明确向应用程序授予此权限。

<permission android:name="android.permission.SYSTEM_ALERT_WINDOW"        android:label="@string/permlab_systemAlertWindow"        android:description="@string/permdesc_systemAlertWindow"        android:protectionLevel="signature|setup|appop|installer|pre23|development" />

        if (useCallingUidState) {           ......            // don't abort if the callingUid has SYSTEM_ALERT_WINDOW permission            if (mService.hasSystemAlertWindowPermission(callingUid,                    callingPid, callingPackage)) {                Slog.w(TAG, "Background activity start for " + callingPackage                        + " allowed because SYSTEM_ALERT_WINDOW permission is granted.");                return false;            }        }

关于areBackgroundActivityStartsAllowed系列

如果此时我们没有 callerApp，则没有向 startActivity() 提供调用者。 基于 PendingIntent 的启动就是这种情况，因为创建者的进程可能未启动且处于活动状态。 如果是这种情况，我们会在调用者允许的情况下为 send() 调用者检索 WindowProcessController，以便我们可以根据其状态做出决定。

// 遗留行为允许使用调用者前台状态绕过 BAL 限制。final boolean balAllowedByPiSender =        PendingIntentRecord.isPendingIntentBalAllowedByCaller(checkedOptions);int callerAppUid = callingUid;if (callerApp == null && balAllowedByPiSender) {    callerApp = mService.getProcessController(realCallingPid, realCallingUid);    callerAppUid = realCallingUid;}if (callerApp != null && useCallingUidState) {    // first check the original calling process    if (callerApp.areBackgroundActivityStartsAllowed(appSwitchState)) {        if (DEBUG_ACTIVITY_STARTS) {            Slog.d(TAG, "Background activity start allowed: callerApp process (pid = "                    + callerApp.getPid() + ", uid = " + callerAppUid + ") is allowed");        }        return false;    }    // only if that one wasn't allowed, check the other ones    final ArraySet<WindowProcessController> uidProcesses =            mService.mProcessMap.getProcesses(callerAppUid);    if (uidProcesses != null) {        for (int i = uidProcesses.size() - 1; i >= 0; i--) {            final WindowProcessController proc = uidProcesses.valueAt(i);            if (proc != callerApp                    && proc.areBackgroundActivityStartsAllowed(appSwitchState)) {                if (DEBUG_ACTIVITY_STARTS) {                    Slog.d(TAG,"Background activity start allowed: process " + proc.getPid()        + " from uid " + callerAppUid + " is allowed");                }                return false;            }        }    }}

应用的某个 Activity 刚在不久前启动/结束

如果不允许应用程序切换，我们将忽略所有启动activity宽限期异常，因此应用程序无法在按下主页按钮后在 onPause() 中自行启动。

在停止应用程序切换的时间之后启动或finish activity的10s内可后台启动Activity

    boolean areBackgroundActivityStartsAllowed(int pid, int uid, String packageName,            int appSwitchState, boolean isCheckingForFgsStart,            boolean hasActivityInVisibleTask, boolean hasBackgroundActivityStartPrivileges,            long lastStopAppSwitchesTime, long lastActivityLaunchTime,            long lastActivityFinishTime) {        if (appSwitchState == APP_SWITCH_ALLOW) {            // 如果调用者中的任何activity最近启动或finish，则允许，            final long now = SystemClock.uptimeMillis();            // 启动或finish有10s宽限            if (now - lastActivityLaunchTime < ACTIVITY_BG_START_GRACE_PERIOD_MS                    || now - lastActivityFinishTime < ACTIVITY_BG_START_GRACE_PERIOD_MS) {                // 得在停止应用程序切换的时间之后启动或finish才行                if (lastActivityLaunchTime > lastStopAppSwitchesTime                        || lastActivityFinishTime > lastStopAppSwitchesTime) {                    if (DEBUG_ACTIVITY_STARTS) {                        Slog.d(TAG, "[Process(" + pid    + ")] Activity start allowed: within "    + ACTIVITY_BG_START_GRACE_PERIOD_MS + "ms grace period");                    }                    return true;                }                if (DEBUG_ACTIVITY_STARTS) {                    Slog.d(TAG, "[Process(" + pid + ")] Activity start within "+ ACTIVITY_BG_START_GRACE_PERIOD_MS+ "ms grace period but also within stop app switch window");                }            }        }

具有后台启动activity特权的Active Instrumentation所在进程

        // Allow if the proc is instrumenting with background activity starts privs.        if (hasBackgroundActivityStartPrivileges) {            if (DEBUG_ACTIVITY_STARTS) {                Slog.d(TAG, "[Process(" + pid                        + ")] Activity start allowed: process instrumenting with background "                        + "activity starts privileges");            }            return true;        }

应用在前台任务的返回栈中拥有 Activity

android U或许会取消

    boolean hasActivityInVisibleTask() {        return (mActivityStateFlags & ACTIVITY_STATE_FLAG_HAS_ACTIVITY_IN_VISIBLE_TASK) != 0;    }

        // Allow if the caller has an activity in any foreground task.        if (hasActivityInVisibleTask                && (appSwitchState == APP_SWITCH_ALLOW || appSwitchState == APP_SWITCH_FG_ONLY)) {            if (DEBUG_ACTIVITY_STARTS) {                Slog.d(TAG, "[Process(" + pid                        + ")] Activity start allowed: process has activity in foreground task");            }            return true;        }

应用中的某个服务被另一个可见应用绑定

请注意，绑定到服务的应用必须保持可见，以便后台应用成功启动 Activity。

        // Allow if the caller is bound by a UID that's currently foreground.        if (isBoundByForegroundUid()) {            if (DEBUG_ACTIVITY_STARTS) {                Slog.d(TAG, "[Process(" + pid                        + ")] Activity start allowed: process bound by foreground uid");            }            return true;        }    private boolean isBoundByForegroundUid() {        synchronized (this) {            if (mBoundClientUids != null) {                for (int i = mBoundClientUids.size() - 1; i >= 0; i--) {                    if (mUidHasActiveVisibleWindowPredicate.test(mBoundClientUids.get(i))) {                        return true;                    }                }            }        }        return false;    }

        @HotPath(caller = HotPath.START_SERVICE)    boolean hasActiveVisibleWindow(int uid) {        if (mVisibleActivityProcessTracker.hasVisibleActivity(uid)) {            return true;        }        return mActiveUids.hasNonAppVisibleWindow(uid);    }

应用收到系统的 PendingIntent 通知

对于服务和广播接收器的挂起 Intent，应用可在该挂起 Intent 发送几秒钟后启动 Activity

应用收到另一个可见应用发送的 PendingIntent

应用的 Service有带BIND_ALLOW_BACKGROUND_ACTIVITY_STARTS的connection

需要声明START_ACTIVITIES_FROM_BACKGROUND权限

Android 10 (API 级别 29) 及更高版本对后台应用可启动 Activity 的时间施加限制。这些限制有助于最大限度地减少对用户造成的中断，并且可以让用户更好地控制其屏幕上显示的内容。
**注意：**为启动 Activity，系统仍会将运行前台服务的应用视为“后台”应用。

详情见BackgroundLaunchProcessController 介绍

        // Allow if the flag was explicitly set.        if (isBackgroundStartAllowedByToken(uid, packageName, isCheckingForFgsStart)) {            if (DEBUG_ACTIVITY_STARTS) {                Slog.d(TAG, "[Process(" + pid                        + ")] Activity start allowed: process allowed by token");            }            return true;        }

应用在具有相同uid的现有Task中启动活动

        // Do not allow background activity start in new task or in a task that uid is not present.        // Also do not allow pinned window to start single instance activity in background,        // as it will recreate the window and makes it to foreground.        boolean blockBalInTask = (newTask                || !targetTask.isUidPresent(mCallingUid)                || (LAUNCH_SINGLE_INSTANCE == mLaunchMode && targetTask.inPinnedWindowingMode()));        if (mRestrictedBgActivity && blockBalInTask && handleBackgroundActivityAbort(r)) {            Slog.e(TAG, "Abort background activity starts from " + mCallingUid);            return START_ABORTED;        }

如何申请豁免

权限相关

申请START_ACTIVITIES_FROM_BACKGROUND 权限

特权system/priv-app/目录下的app才可以申请豁免

<uses-permission android:name="android.permission.START_ACTIVITIES_FROM_BACKGROUND" />

<permissions>    <privapp-permissions package="com.android.xxx">        <permission name="android.permission.START_ACTIVITIES_FROM_BACKGROUND" />     privapp-permissions>permissions>

申请SYSTEM_ALERT_WINDOW权限

**注意：**在 Android 10（Go 版本）上运行的应用无法获得SYSTEM_ALERT_WINDOW权限。
注意：如果应用程序以 API 级别 23 或更高级别为目标，则应用程序用户必须通过权限管理屏幕明确向应用程序授予此权限。

 <uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />

Service有特殊client绑定

应用中的某个服务被另一个可见应用绑定

应用中的某个服务被另一个应用以BIND_ALLOW_BACKGROUND_ACTIVITY_STARTS flag绑定

另一个应用需要声明START_ACTIVITIES_FROM_BACKGROUND权限

来源地址：https://blog.csdn.net/xiaoyantan/article/details/128401740